💧 Water, Polarity, and Density

1. Why is water polar?

Water is polar because of the bent shape of the molecule and the separation of charges: oxygen is slightly negative, and hydrogen is slightly positive.

what is Polar, Dipole, Dipole-Dipole

1. Polar: A molecule with a positive end and a negative end.

2. Dipole: The separation of charges in a polar molecule.

3. Dipole-dipole: Attraction between the positive end of one polar molecule and the negative end of another.

2. What would happen if water were not polar?

• Intermolecular forces would be weaker.

• Water would boil at a lower temperature.

• Ice would not expand when it freezes, so it wouldn’t float.

3. Why is it important that ice floats?

Ice floats on top of water, allowing fish and other aquatic life to survive in the water below.

5. How does kinetic energy relate to temperature?

Temperature is a measure of the average kinetic energy of molecules. Higher kinetic energy means particles move faster.

6. How does salt dissolve in water?

Salt ions are separated by water molecules: the positive ends of water attract negative ions, and the negative ends attract positive ions, allowing the salt to dissolve.

7. What happens to a solid when it melts?

Particles in the solid move faster, bump into each other, and create more space, turning the solid into a liquid.

8. How does density relate to volume and mass?

Density = mass ÷ volume. When volume increases while mass stays the same, density decreases.

9. Why does ice float while most solids sink in liquids?

When water freezes, the molecules form a hexagonal structure with empty spaces, making ice less dense than liquid water.

10. What causes water to expand when it freezes?

The angles and bent shape of water molecules create a hexagonal lattice in ice, which takes up more space.

11. How do dipole forces affect water?

Water molecules are attracted to each other because of their polarity, forming hydrogen bonds that influence its liquid and solid behavior.

12. Why does water contract when it melts?

Melting breaks the hexagonal structure of ice, allowing molecules to move closer together, decreasing volume.

13. What is unique about water’s solid structure?

Ice forms a hexagon with empty spaces, which is why water expands when frozen and contracts when melted.

1. What is the chemical reaction between calcium chloride and sodium carbonate?

CaCl₂ + Na₂CO₃ → CaCO₃ + 2 NaCl

2. What state do the reactants start in?

(calcium chloride and sodium carbonate)

They start as powders or crystals.

3. What happens at the atomic level when the reactants dissolve in water?

The compounds dissolve, dissociate into ions, and react at the atomic level with water molecules separating the ions.

4. How do calcium ions exist in the crystal structure?

5. What is the total ionic equation for the reaction?

Ca²⁺ + 2 Cl⁻ + 2 Na⁺ + CO₃²⁻ → CaCO₃ (s) + 2 Na⁺ + 2 Cl⁻

6. How do you get the net ionic equation?

Cancel out the spectator ions (Na⁺ and Cl⁻) that do not participate in forming the solid:

Ca²⁺ + CO₃²⁻ → CaCO₃ (s)

7. What are spectator ions?

Spectator ions are ions present in the solution that do not participate in the actual chemical reaction.